The energy supply in the world cannot satisfy the great demand with each passing day, and the recovery of the energy becomes more and more important. At present, the world pays much attention on recovery and utilization of the energy from, such as the boiler, the primary reformer of large chemical fertilizer plant.
The primary reformer of large chemical fertilizer plant comprises: a radiation section; a convection section; an auxiliary boiler and a common flue chimney etc. The radiation section has a configuration of box structure wherein a plurality of conversion tubes, loaded with catalysis for converting reaction of the hydrogen generation between the naphtha gas and the steam, are installed. At the top of the reformer, a plurality of burners are installed and burns vertically downward, providing the heat for the converting reaction. The flue gas passes through the lower part of the radiation section, enters into the high-temperature side of the convection section, at the top of the convection section mixes with the flue gas coming from the auxiliary boiler, and finally comes into the low-temperature side of the convection section. The temperature of the flue gas may be as high as about 300.degree. C. when it leaves the convection section. Then the flue gas, drawn by a flue gas fan, will be exhausted through the flue chimney to the atmosphere.
As the temperature of the exhaust gas is relatively high, its direct exhaustion will cause the heat loss and the pollution of the environment. On the other hand, the wall temperature of the radiation section can be as high as from about 80.degree.-120.degree. C., and the environment temperature at the top of the reformer can be as high as from 50.degree. C.-60.degree. C.
Traditionally, a rotary air heat exchanger is preferably employed, for the primary reformer in large chemical fertilizer plants. A plurality of metal plates as heat-accumulator are disposed on the rotor of the heat exchanger. When the rotor of the air heat exchanger turns into the flue, the metal accumulator-plates absorb the heat of the flue gas, and the temperature of the metal plates increase. As the metal plates turn out from the flue and enter into the air duct, the rotor release its accumulated heat to the air and its temperature drops. The rotation of the rotor is continued and the rotor enters into the flue, the metal plates transfer the heat of flue gas to the air by alternation of the heat-absorbing and releasing of the rotor. The main disadvantages of such kind of heat exchanger are: the series leakage of the air (8% is the designed value, but a range of 12-18% is in practice); the metal plates are passed through the cold air side alternatively; the super cooling zone of the rotor can not be avoided, and it is difficult to avoid the dew point corrosion and the ash choke of the heat exchanger; the high head loss (1200-1600 Pa) due to the small gap between metal plates; power consumed by the rotor; high cost for maintenance; reformer accident caused by the stop of the rotary pre-heater, and disability to reduce the environmental temperature at the top of the reformer.